FBS Blood Test Results Explained


The FBS blood test is a fasting blood sugar test. It is used to determine what the ongoing blood glucose levels happen to be when food is not being digested and distributed to the rest of the body. This can detect high blood glucose, low blood glucose, and is often used as a screen for diabetes when the signs and symptoms of the disease are present.

It is also used to determine gestational diabetes, prediabetes, and to monitor glucose levels for those who have already been diagnosed with the condition.

The FBS blood test requires fasting for a minimum of 8 hours to be effective. For this reason, it is most often given early in the morning to avoid fasting issues during daytime hours.

When Is the FBS Blood Test Ordered?

It is recommended that anyone above the age of 45 receive regular diabetes screening or whenever an individual has potential risk factors that may encourage diabetes development. Part of the screening process would include the FBS blood test.

There are several risk factors which may be deemed as a qualifying factor by an individual’s medical provider. One of the most common risk factors is being physically inactive, overweight, or obese as determined by a BMI measurement.

Having a close relative with diabetes is also considered a qualifying risk factor for most individuals. Women who have delivered a baby weighing more than 9 pounds, having polycystic ovarian syndrome, or being in a high-risk culture or ethnicity are also risk factors that will be considered.

Someone with high blood pressure of 140/90 with the above risk factors may be considered to be at a higher risk of diabetes development and may be placed on a pre-diabetic treatment plan even if the FBS blood test comes back as normal.

It may also be ordered when the signs and symptoms of inappropriate glucose levels are present. This may include increased thirst, ongoing fatigue, blurred vision, or slow healing wounds. Frequent hunger, trembling, anxiety, confusion, and sweating without another explanation may also be evidence of a glucose disorder.

What Do My FBS Test Results Mean?

If you’ve been given an FBS blood test, then any result which is between 77-99 mg/dL is considered to be a normal fasting glucose level. Some laboratories may report test results in mmol/L instead of mg/dL, so a normal result in that measurement would be 3.9-5.5.

For individuals who have a fasting glucose level of 100-125 mg/dL or 5.6-6.9 mmol/L, then this is generally considered to be evidence of prediabetes. It may also be called an “impaired fasting glucose.” Action will be taken to limit sugar intake and improve physical activity for many patients who receive an FBS blood test result like this one.

Any fasting blood glucose test results that are above 126 mg/dL or 7 mmol/L which occurs on more than one testing occasion is considered enough evidence to diagnose an individual with diabetes.

Here’s What You Need to Know

If you’ve received a high FBS blood test result, diabetes isn’t always the culprit behind the abnormal reading. Someone suffering from acute stress may have an elevated blood glucose level. Certain chronic kidney diseases, pancreatitis, and Cushing syndrome have also been known to present with a high FBS reading. Certain cancers have also been known to affect blood sugar readings.

The primary cause of a high FBS blood test result, however, is the excessive consumption of food. Eating a large meal just before the 8-hour fasting period can affect the blood test results.

Low FBS blood test results can also be caused by certain lifestyle choices or diseases. The most common reason for an abnormally low FBS reading is excessive alcohol consumption. Individuals suffering from severe liver disease or an adrenal insufficiency will also see test results that are lower than normal.

Certain conditions involving the thyroid are also known to interfere with the FBS blood test. Individuals who practice prolonged fasting for religious purposes have also been known to have abnormally low test results without any other health issue.

Here’s What You Need to Know

Do not under-estimate the effects that stress can have on the body in terms of glucose levels. Extreme stress has been proven to cause glucose spikes.

Certain medications have also been known to interfere with blood glucose readings. Taking drugs like acetaminophen have been known to decrease glucose, while estrogens, lithium, and diuretics have been known to increase glucose levels.

The FBS blood test is a proven way to detect diabetes and other metabolism disorders or chronic diseases. Ask your doctor today if this blood test would be right for you.